Role of doped Ru in coercivity-enhanced La$_{0.6}$Sr$_{0.4}MnO$_3$ thin film studied by x-ray magnetic circular dichroism

摘要

The coercivity of La$_{1-x}$Sr$_x$MnO$_3$ thin films can be enhanced by Rusubstitution for Mn. In order to elucidate its mechanism, we performed softx-ray absorption and magnetic circular dichroism measurements at the RuM$_{2,3}$ and Mn L$_{2,3}$ edges. We found that the spin direction of Ru and Mnare opposite and that Ru has a finite orbital magnetic moment. Cluster-modelanalysis indicated that the finite orbital magnetic moment as well as thereduced spin moment of Ru result from local lattice distortion caused byepitaxial strain from the SrTiO$_3$ substrate in the presence of spin-orbitinteraction.